The present invention relates to a method for controlling a vehicle comprising a dump body. The invention also relates to a device for controlling a vehicle comprising a dump body. Further, the invention relates to different types of vehicles having a tiltable dump body, such as a dump truck or an articulated hauler. In connection with transportation of heavy loads, e.g. in contracting work, a work machine of the type of an articulated hauler is frequently used. Such vehicles may be operated with large and heavy loads in areas where there are no roads, for example for transports in connection with road or tunnel building, sand pits, mines and similar environments.
An articulated hauler comprises a hydraulic system for moving the tiltable dump body between a lowered position and a raised position. The dump body is connected to the vehicle frame via a hinge at the rear of the vehicle and two hydraulic cylinders are arranged between the frame and the dump body for tilting the dump body.
Conventionally, an operator of the vehicle controls the tilting procedure by operating a control element, such as a tilt lever. During a tilting operation, the dump body is raised to its extreme limit (fully raised position) and then returned to its home position (fully lowered position).
An articulated hauler is often used in a repeated work cycle. The term “work cycle” comprises a route of the work machine (ie the work cycle travel path) and tilting of the dump body. The work cycle is repeated in the same geographical area. According to a work cycle example, an articulated hauler is loaded at a first position, driven along a varied route, unloaded at a second position and driven back along the varied route. Normally, an excavator or wheel loader loads the container of the dump truck at the first position. The articulated hauler is unloaded by means of tilting the dump body.
EP 1 286 850 B1 discloses a semi-automatic system for facilitating operation of an articulated hauler during a tilting procedure. According to this system, a brake is automatically activated and the gearbox is automatically controlled to a neutral position when the operator pushes a tilting activation button.
It is desirable to achieve a method which creates conditions for increasing productivity by shortening a work cycle time.
A method according to an aspect of the present invention includes the steps of monitoring the contents of the dump body during an elevating motion, determining when the dump body has reached a predefined condition during the elevating motion, and controlling the vehicle when it is determined that the dump body has reached the predefined condition.
The terms “monitoring the dump body during an elevating motion” refers to monitoring the extent of contents in the dump body either directly or indirectly.
According to a preferred embodiment, the predefined condition is defined as an empty state. The term “empty state” represents a condition where substantially all material/soil has left the interior of the dump body. Thus, the elevating motion may be interrupted as soon as the dump body is emptied. Since the dump body in many cases is emptied at a tilting angle substantially smaller than the maximum tilting angle, the total tilting cycle time is substantially shortened.
According to an alternative embodiment, the predefined condition is defined as the point in time when the material in the dump body starts to slide out of the dump body. This embodiment may be advantageous when operating material which easily slides once it is in motion. An example of such material is gravel. Thus, the elevating motion may be stopped as soon as the material is in motion and maintained in that position until all material has left the dump body.
The method creates conditions for increasing both productivity and safety due to the facilitated operation. This advantage is especially pronounced for unexperienced operators.
Further, the terms “controlling the vehicle” refers to any control, such as controlling the operation/movement of the dump body and/or other vehicle systems, such as a powertrain for propelling the vehicle. Preferably, the dumping procedure is controlled. For example, the powertrain may be operated for propelling the vehicle in such a manner that the material is dumped in a controlled way over a certain distance, preferably in an even layer, on the ground. Preferably, the vehicle is forwarded with a certain speed. Further, the operation/movement of the dump body and the powertrain may be operated simultaneously.
According to a preferred embodiment, the method comprises the step of lowering the dump body when it is determined that the dump body has reached the empty state. By automatically lowering the dump body immediately after it has been emptied, the total tilting cycle time is further shortened.
Preferably, the method comprises the step of monitoring a load receiving part of the dump body during the elevating motion and determining whether the dump body is empty on the basis of the detection. Thus, an interior of the dump body is monitored in order to determine when the dump body is emptied.
According to a further preferred embodiment, the method comprises the step of detecting a pressure in a hydraulic cylinder adapted to operate the dump body and determining whether the dump body has reached the predefined condition on the basis of the pressure detection. Preferably, the method comprises the step of establishing said predefined condition when a certain pressure change is detected. The pressure change is preferably predefined and is set to indicate the predefined condition.
It is desirable to achieve a device which creates conditions for increasing productivity by shortening a work cycle time.
A device according to an aspect of the present invention comprises means for automatically monitoring the contents of the dump body during an elevating motion, and means adapted to determine when the dump body has reached a predefined condition during the elevating motion and control the vehicle when it is determined that the dump body has reached the predefined condition. Other advantageous features and functions of various embodiments of the invention are set